AQA · A-Level · Biology
Course version: 7402 · Version from Sept 2016
The difference between magnification and resolution.
Full specification wording
Methods of studying cells: The difference between magnification and resolution.
Magnification is how many times larger the image is than the real object (size of image divided by size of real object).
Checked against the AQA 7402 specification (opens in a new tab) on .
- Point 3 of 4
- 4 key terms
Study notes
From the checked teaching notes for this specification point.
The idea
Magnification is how many times larger the image is than the real object (size of image divided by size of real object). It is a ratio with no units. While it can be increased mathematically, useful magnification is limited by resolution. Resolution is the minimum distance two points can be apart and still be distinguished as separate. It is a distance, measured in micrometres or nanometres, determined by the wavelength of the radiation used. The practical consequence is that magnifying beyond the resolving power produces a larger but blurred image, revealing no new detail, known as empty magnification. This is why ribosomes and membrane details remained invisible until electron microscopy, as electrons have a much shorter wavelength than light, providing higher resolution.
What earns the marks
- Defining magnification as the number of times larger the image is than the object (size of image divided by size of real object).
- Defining resolution as the minimum distance at which two points can still be distinguished as separate.
- Stating resolution is limited by the wavelength of radiation, meaning electron microscopes resolve more detail than optical microscopes.
- Explaining that increasing magnification beyond the resolving power gives a larger but no clearer image (empty magnification).
- Quoting resolution with a unit of distance and magnification without any unit.
Common mistakes and how to put them right
Writing magnification where the question requires resolution, such as when discussing the ability to see detail.
Defining resolution merely as clarity or amount of detail, without the specific idea of distinguishing two separate points.
Giving magnification a unit such as micrometres.
Put it right: Magnification is a ratio and has no units.
Stating an electron microscope resolves better because it magnifies more, rather than because electrons have a shorter wavelength.
Exam tips
- If a question asks about what can be seen or told apart, the answer is resolution; if it asks about how much bigger, it is magnification.
- In an explanation question, name the shorter wavelength of electrons as the cause for higher resolution in electron microscopes.
Try the lesson
The start of the Methods of studying cells: The difference between magnification and resolution. lesson, made from checked teaching notes for this specification point.
Have a go first
Which statement describes magnification rather than resolution?
Listen
Magnification is how many times larger the image is than the real object (size of image divided by size of real object). It is a ratio with no units. While it can be increased mathematically, useful magnification is limited by resolution. Resolution is the minimum distance two points can be apart and still be distinguished as separate. It is a distance, measured in micrometres or nanometres, determined by the wavelength of the radiation used. The practical consequence is that magnifying beyond the resolving power produces a larger but blurred image, revealing no new detail, known as empty magnification. This is why ribosomes and membrane details remained invisible until electron microscopy, as electrons have a much shorter wavelength than light, providing higher resolution. A strong answer earns marks for these points. defining magnification as the number of times larger the image is than the object (size of image divided by size of real object). defining resolution as the minimum distance at which two points can still be distinguished as separate. stating resolution is limited by the wavelength of radiation, meaning electron microscopes resolve more detail than optical microscopes. explaining that increasing magnification beyond the resolving power gives a larger but no clearer image (empty magnification). Exam tip: If a question asks about what can be seen or told apart, the answer is resolution; if it asks about how much bigger, it is magnification.
Key words
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magnification
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resolution
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empty magnification
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wavelength limit
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See every definition
- magnification
- How many times larger the image is than the real object, calculated as size of image divided by size of real object; it is a ratio with no units.
- resolution
- The minimum distance two points can be apart and still be distinguished as separate, measured in micrometres or nanometres and determined by the wavelength of the radiation used.
- empty magnification
- Magnifying beyond the resolving power, which produces a larger but blurred image revealing no new detail.
- wavelength limit
- Resolution is determined by the wavelength of the radiation used, so electrons having a much shorter wavelength than light provide higher resolution.
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